Hello!! It’s great to see you getting an idea of costs. Here are some insights into more specific costs per team position. I’m a webcomic assistant for a couple different projects including an upcoming Webtoon Original. These rates may vary based on the persons experience and the art style.
For Line art (I work with a moderately complex style):
$5/panel + $2/extra character
I don’t do backgrounds or effects. This is based on how fast I work, and complexity, and is subject to change with each artist/style.
For flat coloring:
$3/panel + $1/extra character
For shading (depending on the shading style):
$3-$5/panel + $2/extra character
I always say that these rates are open to negotiation since I don’t know the financial situations of the artist. There are normally no issues with these rates, and they’re accepted most often.
Keep in mind though, while these may seem low at first, 60 panels lineart with 1 person is $300, and since a webcomic can’t just have one person per panel, it’s definitely higher.
Hope this helps!! Good luck!